Fuse plug circuit breaker



NGV. 279 1951 E v SUNDT 257698315 FUSE PLUG CIRCUIT BREAKER Filed May 6, 1946 2 SI-IEETS-SHEET l gf... w26

INVENTOR.' EDM/Ae@ T/f SUA/0T.

Num 279 1951 E, v, SUNDT 2,576,815

FUSE'PLUG CIRCUIT BREAKER Filed May 6, 1946 2 SHEETS-SHEET 2 A JNVENTOR: EDM/Aap PT SUA/.D77

(5 Wwf/Zim Patented Nov. 27,v 1951 UNITED STATES PATENT OFFICE FUSE PLUG CIRCUITy BREAKER. Edward v. sunatf. chicago, 111.

Applicatian May c, 194s, serial No. 667,546

claims. (C1. 20o- 116) The invention relates to circuit breakers and has particular reference to a very compact circuit breaker small enough to be inserted into an ordinary fuse socket.

Ordinary fuse plugs with a fusible metal insert have usually been resorted to for purposes for economy and convenience. Their most widespread use has been in house wiring circuits and similar types of circuits where the load on the electric system is not excessive. Fuse plugs of this type have the disadvantage in that once blown out the fuse plug must be thrown away and` replaced with a new one.

Circuit breakers have long been known and have the advantage of being capable of resetting after they have been released to break the circuit because of an overload condition. Consequently, circuit breakers are capable offbeing used over and over again. On the other hand, circuit breakers have had the disadvantage in the past of being relatively high in initial c-ost which has prevented widespread use of them where loads are light and the cost of installation is a primary factor. Y

It is-,therefora among the'objects of the inventionto provide a new and improved circuit breaker which issufliciently compact and inexpensive -so that it can be used interchangeably with ordinary fuse plugs.

Another object of the invention is to provide a circuit breaker of such inexpensive construction that it can be used with economy in circuits where the load is light and the wiring is not extensive.

Still another object is to provide a circuit breaker for ordinary light capacity circuits which must be removed from the circuit before it is reset following the breaking of a circuit because of a short or an excessive load on the line.

The objects further contemplate a small compact' plug type circuit breaker which is provided with a visible indicator to indicate when the breaker has been released and which also incorporates a means for adjusting they circuit breaker so that it can be' actuated at different loads. y

Further incorporated into the device is the provision of a means for reducing or minimizing arcing or flash when the circuit is broken or in the event that an attempt might be made to replace the device while the circuit is still shorted.

With these and other objects in View, the invention consists in the construction, arrangement and combination of the various parts of the device whereby the objects contemplated arel attained, as hereinafter more fully set forth, pointed out in the claims and illustrated in the accompanying drawings, in which:

Figure l is a longitudinal, sectional view of the device showing the circuit breaker in place in a fuse plug socket.

Figure 2 is a longitudinal, sectional view at right angles to the View shown in Figure 1 and taken on the line 2-2 of Figure l showing the circuit breaker removed from the socket.

Figure 3 is a cross-sectional View taken on the line 3 3 of Figure 1.

Figure 4 is alongitudinal view partly in section showing the circuit breaker in released position.-

Figure 5 is a perspective view of the bimetallic element.

Figure 6 is an exploded view showing the parts which go to make up the circuit breaker.

Figure '7 is a top view of a modified form of the device incorporating an adjusting feature.

Figure 8 is a longitudinal View partially in section of the modified form taken on the line B-B 0f Figure 7.

Figure 9 is a longitudinal view partially in section showing Still another modified form.

Heretofore it has been thought that in order to provide circuit breakers which would satisfy all of the requirements of a device for safely breaking the circuit under overload conditions that the mechanical parts of the device must be of heavy, rugged construction. Little thought has been given to economy of space and economy in the use of materials permitting the circuit breaker to be installed on volts lines in ordinary lighting or light power circuits. To date the design of circuit breakers has been such that they could not be readily adapted to installations where they could satisfactorily substitute for the ordinary inexpensive fusible plug.

In an embodiment chosen to illustrate a compact design for a circuit breaker which is capable of being placed in the precise fixture originally designed for a fuse plug there is shown such a iixture comprising a base il] of insulating material, a shell II of similar material and a metal screw socket I2 mounted within the shell II. A binding post i3 is attached to a connection I4 communicating with the screw socket, and a binding post i5 is attached to a lead IS which extends to the center of the screw socket.

The circuit breaker` itself comprises a molded shell or casing il having' a reduced portion I8 and an enlarged or head portion i9. Within the molded shell I1 is a chamber 23 occupying the areas for the circuit breaker.

acter 26 in position at the bottom of the chamber 20.

As clearly shown in Figure 5, the bimetallic member comprises a bracket 21 constitutinga base in which is a centralaperture 28 adapted to receive the eyelet 25. At one endv 'of the bracket is an outwardly extending leg ,29, an outer` portion of which terminates in a hooked'endor extension 30. A second leg 3l is joined" to the leg 29 adjacent the portion incorporating the hooked extension and extends inwardly to a point 32adjacent to but spaced from the end of the bracket to which the Yleg 29 is attached. At the point 32 a resilientV arm 33 is attached to the leg 3l 'sothat there isa continuous electric connection. The arm is bowed around and has attached at its other end a bracket 34, the arm being provided with a recess 35 which assists in locating the bimetallic member by means of engagement with a rib 35 on the Wall of the charnber 20. The bracket 34 has a platform 31 at the outer end which is adapted to rest upon a shelf .orshoulder 38 and further assist in positively locating the bimeiallic member.

The platform 31 provides one of two contact On the side of the chamber opposite from the platform 31 isla right angular element 39 providing a second contact area, the right angular element having a leg 40 which extends along the outside surface of the reduced portion of the molded shell. A metallic Ascrew shell 4| surrounds the reduced portion of the molded shell and isvlocated in electric contact with the leg 40. The screw shell has an in- ,Wardly turned flange 42 of the conventional sort and snuglyuts around the reduced portion or the molded shell so that it cannot be readily removed. Within the chamber are parts of a movable device which constitute a latch member'adapted to break'the circuit. This includes a guide post 45which extends axially throughout the length ofthe'rnolded shell l1. The guide post has a The reset button extends slideably through a central aperture 49 in the cover and slides a limited distance relative t thereto.

Contact is made between contact areas at 31 and39 by means of a saddle 50. The saddle has a cup shaped central portion I centrally aper- Vtured so that it is adapted to slide over the outer end of the guide post and has one wing 52 'adapted to rest upon the platform 31 and a wing 53 adapted to rest upon the angular element"39. A coiled spring 55 bears at its lower end against vthe inside end of the eyelet 25 and against a washer 56 which abuts the bottom of the cup shaped portion of the saddle. A second coiled spring 51, somewhat heavier than the first, rests in the bottom of the cup shaped portion 5l of areas at 31 and 39.*

4 the saddle on the side of the saddle opposite from the rst spring.

Also located on the guide post surrounding the larger portion is a transverse latch element here illustrated as a disc 58, and beneath the disc is an insulating washer 54 separating the disc from the spring 51. The latch disc has a shank 59 on the outer side which slideably engages the interior of the setting button 41. It will be noted that the disc 58 has an undercut outer edge and that a portion of the edge, as viewed at the left side of Figure 2, is notched as at 60 so that the walls of the notch may engage a projection r(il `onpthe interior of the chamber 20 for positioning and guiding the latch disc during its operation. The saddle is also provided with a notch 62 which likewise is adapted to engage and YVto be guided' by the projection 6I.

In operatori the latch disc is normally set in the closed position best shown in Figure 2. In

this position the hook end 30 overlies and engages the outer edge ofthe latch disc. Both Ysprings ,5,5 and 51 are contracted. The spring 55 tends to press upwardly against the saddle but the'tendency is overcome by the greater pressure of the spring 51 which tends to press the saddle inwardly into apposition where the wings 52 and 53 are in snug lelectric contact with the contact d ln this adjustment current is adapted to iiow from the binding post I5 through the eyelet 25, thence to the bracket 21VY through the leg 29Y of the bimetallic element,'then through the leg 3l,

the arm 33the bracket 34 and inally through the saddle to the right angular element 39 lfrom whence it passes to the screw shell 4i and to the binding post I3. InV this position of the, saddle the circuit is complete through the bimetallic member. n d d When there is an overload in the line, the line heats up and so,lalso, the bimetallic member 26. As the legs 29 and 3| heat up they tend to bow f outwardly so/'that the Vhooked extension 30 disengages itself from the edge ofthe latch disc. When disengagement is complete the latch disc is ,.released, and the spring 55 `then pushes the saddle outwardly so that the wings are disconnected from the contact areas and the circuit isbroken.

At the same time the spring 515presses the latch disc,V in company with the setting button,out

Awardly to the position shown in V,Figure 4 sc as to afford a visual indication of the fact that*A the circuit isbroken. g

'Inasmuch as there is a certain limited freedom lof motionbetween the inside of the cup shaped t portion of the setting buttonand the end of the flange on the latch disc, it is not possible to re- :set the latch disc beneath the hooked extension of the bimetallic member solong as theycircuit breaker remains in position in the fixture.

In order to' press the setting button inwardly, together with the guide, post, far enough to reset the latch, the guide post must extend inwardlyV to theV position shown in Figure 2. This is not possible when theguide post is prevented ircpifn extending inwardly by contact with the bottom of the xture or socket. VYOnce the latch discY has been set the circuit breaker may Vbe screwed into the xture or socket, and contact of the bottom of the guide post withthe bottom of the fixture or socket will tend to lift the setting button a means is provided ,for .Shifting thelawh disc .in

such a manner that it will engage to a greater or lesser extent beneath the hooked end of the bimetallic member. By this device the circuit breaker may be set to release itself at a greater or lesser load increase, depending upon requirements.

In the modified form the principal operative parts of the device as a whole remain the same and are housed within the samel molded shell. In order to provide an adjustment, however, the aperture de in a cover 23 is made slightly eccentric as is particularly apparent in Figure 7. The cover is designed to be held somewhat loosely in place at the top of the molded shell by means of a ilanged ring 24 which is provided with a pointer le at one side. So that the pointer may remain in fixed` position at all times, the molded shell is provided with a recess lll within which a projection T5 on the flanged ring is designed to engage The cover is provided withV holes l", for example, to which an instrument may be applied in order to rotate the cover.

Rotation of the cover changes the relative position of the eccentric aperture in the center. As the aperture shifts from one side toward the other the guide post will be tilted slightly from one substantially vertical position to another and thus change the location of the disc 53 relative to theY hooked end 3d of the bimetanic element.

For example, in setting of the device illustrated in Figures 7 and 8 the eccentricJ aperture in the cover is moved to an intermediate position toward the left, and in this position the pointer 'Hl will coincide with a calibration i3 on the cover. At this settingA the` device will release under a load of intermediate magnitude.

To set theA device for release under a heavy load, the cover is rotated, clockwise, until a cali'- bration Til coincides with the pointer. At this adjustment the eccentric aperture in the cover will have shifted toward the right, as viewed in Figure 8, although there may be some lateral shift with respect to the location of the bimetallic element, A shifted position is indicated by the dotted lines in Figure 8. Tilting the guide post moves the disc 58 so that it underlies the hooked end a greater amount. This means that in order to release the circuit breaker the load must be greater and cause a greater heating and subsequent bending of the bimetallic element.

Another intermediate release mayl be accomplished by setting the calibration l2 opposite the pointer lil, whereas, for lightest load a calibration ll should lie opposite the pointer. By this simple means, therefore, the same circuit breaker can be set for release at various loads.

Although the circuit breaker has been shown primarily as one designed for incorporation into a molded shell of the size of a fuse plug, the same principles of design and construction could be incorporated into a circuit breaker having a casing of different proportions. An example of the latter construction is shown in Figure 9 wherein an insulating base 8? is provided with a housing El secured thereto which is adapted to receive complementary portions 82 andY 83 of a casing housing moving parts of the circuit breaker. Within the casing is providedV a bimetallic element having a shape and construction similar to that described in the preferred embodiment and a Contact bracket 85 making opposite points of contact for the wings of the saddle 50 in the manner described in connection with the preferred embodiment. The resetting button 51 and latch disc 58 function with the bimetallic element in the same manner as previously described.

Among the distinctions in the modified form shown in Figure 9 is the absence of a screw socket and the substitution therefor of contacts held in place by i'langes at the edges of the complementary parts of the casing which in turn are anchored by the housing 8| secured to the base by screws 86.

By the provision of a circuit breaker in the compact design shown individual parts may be reduced to a minimum and made of inexpensive materials. Moving parts of the device are coniined to a single member, and all are coaxially located about a single guide post. Assembly operations are thereby reduced substantially to a minimum, and there is provided an inexpensive circuit breaker which can be used in fixtures already designed for the reception of fuse plugs, the circuit breaker being capable of a simple resetting operation but with the added provision of making it necessary to remove the breaker from the short circuited line before the resetting operation is capable of being completed.

Although the invention has been herein shown and described in what is conceived to be the most practical and preferred embodiment, it is recognized that departures may be made therefrom within the scope of the invention, which is not to be limited to the details disclosed herein but is to be accorded the full scope of the claims so as to embrace any and all equivalent structures.

The invention having been herein described, what is claimed and sought to be secured by Letters Patent is:

l. An electrical circuit breaker comprising a casing having a chamber therein, a first contact element on one side of the chamber and providing an external electrical connection, a second contact element on the opposite side of the chamber, a third contact element on another side of the chamber and providing another external electrical connection, a bimetallic thermostat element in the chamber having a latch shoulder and electrically connected between the second and third contact elements, a movable saddle adapted to engage and disengage the iirst and second contact elements to make and break an electric circuit between the first and third contact elements and through the bimetallic thermo-stat element, a spring engaging the saddle and adapted to disengage the saddle from the rst and second contact elements, a movable latch member adapted to be latched by the latch shoulder oi the birnetallic thermostat element, and a second spring between the latch member and the saddle for engaging the saddle with the first and second Contact elements against the action of the rst spring when the latch member is latched.

2. An electrical circuit breaker comprising a casing having a chamber therein, a rst contact element on one side of the chamber and providing an external electrical connection, a second contact element on the opposite side or" the chamber, a third contact element on another side of the chamber and providing anotherl external electrical connection, a bimetallic thermostat element in the chamber having a latch shoulder and electrically connected between the second and third contact elements, a movable saddle adapted to engage and disengage the first and second contact elements to make and break an electric circuit between the rst and third con- 'tactY elements and through the bimetallic thermo- -stat element, a spring engaging the saddle and adapted to disengage the saddle from the first and second contact'elernents, Va movable Vlatch member adapted to be latchedv by the latch shoulder of the bimetallic thermostat element, a second spring between the'latch member and the saddle for engaging the saddle Ywith the rst and second contact elementsagainst the action of the first spring when the, latch member is latched, and an externally manipulated button extending into the 'chamber for moving the latch member into latching position. Y l Y 3. An electric circuit breaker adapted to screw into a1 fuse Vsocket comprising a casingl having a chamber therein, aiscrewshell on the exterior of the casing, Va first -contact element on one sideof the chamber electrically connected to the screw shell, a second contact element on theopposite side of the chamber, an eyelet extending through the bottom of the casing andV forming a third vcontact element, a bimetallic thermostat element in the chamber having a latch shoulder and electrically connected between the second and third contact elements, a movable saddle adapted to engage and disengage the rst and second contact elements to make and break an electric circuit between the rst and third contact elements and through the bimetallic thermostat element, a spring adapted to disengage the saddle from the first` and second contact elements, a movable latch member adapted to be latched by the shoulder of the bimetallic thermostat element, a second spring between the latch member and the saddle for engaging thesaddle with the rst and second Vcontact elements against the action of the first spring when the latch member is latched,y anV externally manipulated button extending into the chamber for moving the latch member into latching position, and a post extending in said eyelet and engaging the button to prevent latching of the latch member and reengagement of the saddle with the rst and second contact elements when the electrical circuit breaker is tightly screwed into the fuse socket. Y

4. An electric circuit breaker adapted to screw into a fuse socket comprising an insulating shell having a portion adapted to t within a fuse socket and a chamber within the shell, a screw shell affixed to the insulating shell making an electrical contact for connection with the socket, a bottom contact eyelet at the center of the bottom of said insulating shell making an electrical contact for connection with the socket, a bimetallic thermostat element secured within the chamber by said eyelet and having a hooked extension and a contact element, an apertured top for the chamber, a central guide post having one end slidable endwise in said eyelet and the other end being slidable in the aperture of said top, a saddle slidably mounted on said guide post having ends in releasable electric communication respectively with the contact element and the screw shell, a latch element on said guide post having a portion releasably engaged beneath the hooked extension when in a set position, and opposed springs interposed between the saddle and adjacent portions of the circuit breaker adapted respectively to. hold the saddle in electrical communicating and released positions.v Y

5. An electrical circuitv breaker adapted to screw into a fuse socket comprising an insulated shell having avportion adapted -to fit within a liess socket; ahead porties .aus .a chamber, witnin said shell, a screw shell afxed to said rst portion making one electrical contact for engagement with the socket, a bottom contact eyelet at the center of the bottom-of said shell making another electrical contact for engagement with the socket, a bimetallic thermostat element secured within the chamber by said eyelet having a hooked extension and a contact element, an apertured top for the chamber, a central guide post having one end slidable in said eyelet and the other end slidably received in the aperture in said top, a saddle slidably mounted on said guide post having opposite ends in releasable electric communication respectively with the contact element and the screw shell, a latch disc on said guide post having a lip releasably engaged beneath the hooked extension when in a set position, and opposed springs of different tension positioned between the saddle and respectivelyV the latch disc and the eyelet adapted respectively to hold the saddle in electrical communicating and in released positions.

6. An electrical circuit breaker adapted to screw into a fuse socket comprising a casing, a screw shell on the exterior of the casing forming one electrical connection to the fuse socket, a central eyelet on the casing forming another electrical connection to the fuse socket, a releasable overload switch in the casing includingV a contact member movable to electrically connect the eyelet and the screw shell, means for actuating said releasable overload switch including a post member slidably mounted in the casing and on which post member the contact member is slidably mounted, said post member being of greater length than the casing so that at least one terminal portion of the post member extends from the casing at all times, spring means mounted on the post member at opposite sides of the contact member, means carried by the post member and operable through one of said springs when the post member is moved in one direction to move the contact member to circuit closing position, current responsive latch means for engaging said contact member moving means to latch the contact member in circuit closing position against the tension of the other of said spring means, a button engaging one end of the post member and extending through a wall of the casing at all times for so moving the post member, the opposite end of the post member being projected from said casing within the area thereof which is adapted to be received in said fuse socket when in service, before the contact member moving means of the post member reaches latched position whereby to prevent closing the circuit breaker when the casing iswithin such socket, and a lost motion connection between the post member and said contact member moving means to permit sliding movement of the post member in the opposite direction after the latch is engaged.

7. In an electric circuit breaker, a substantially cylindrical shell member having a cavity, spaced electric contact elements in said cavity, a post assembly mounted in said cavity and axially slidable with respect to the shell, said post assembly including a post member having Vone end thereof disposed substantially on the axis of the shell, a contact member, and a latch member, the contact member and the latch member being slidably mounted on the post member, said post assembly when the circuit breaker is in service, being normally latched in position in which the contact member is in circuit closing relationship with said contact elements, a spring urging the post assembly and said contact member out of circuit closing relation, a guide member in said shell forthe other end of the post member, said guide member having a guide opening in which said other end of the post is engaged, said opening being eccentrically disposed relative to the axis of the shell and guiding the axially slidable movement of the post, a bimetallic hook member mounted in said shell and in circuit with said contact elements, said ,hook member having a portion in overlying,

transversely slidable engagement with the latch member of the post assembly and adapted to bow out of engagement therewith under the heating influence of an increased electric current owing through the hook member, means mounting said post guide member for rotation about the axis of the shell, said guide member having a plurality of settings for varying the degree of overlapping engagement between the hook and the latch member of the post assembly for release of the engagement at different current loads.

8. In an electric circuit breaker a shell having a cylindrical side w-all, a bottom, and a cover rotatably mounted relative to the side wall, said bottom having a central aperture therein and said cover having an eccentrically located aperture therethrough, -a pair of electric contact elements in said shell, a post extending slidably through said apertures, a contact member mounted on said post and movable to circuit-closing relationship with said contact elements when the post is moved in one direction, and a spring normally urging said post in the opposite direction and said contact member out o circuit closing relationship, shoulder means on said post, a bimetallic hook in circuit with said contact elements and mounted in the shell, said hook having a portion overlying and in transversely slidable engagement with the shoulder means and adapted to bow out of engagement under the heating influence of an increase in electric current iiowing therethrough, said cover having a plurality of positions of rotative adjustment for varying the degree of eccentricity of said post and the shoulder means thereon, with respect to the axis of the shell to thereby adjust the degree or" overlap of said hook and shoulder means to provide for release of the hook at diierent current loads.

9. In an electric circuit breaker comprising an insulating shell having a chamber therein, a cover for the chamber, electric current controlling contact elements and a current carrying assembly including a bimetallic member in circuit with the contact elements and having a latch hook thereon, the combination of a contact operating and position indicating latching unit disposed within the chamber and including a post member and a contact member slidably mounted thereon, and means for operating the Contact member to and from circuit closing position with respect to the contact elements, a latch member slidably mounted on the post member for engaging the latch hook, said latch member having a i with said latch hook and the contact member into circuit closing position with the Contact elements, and being movable by said latch member moving means to an extended position beyond the cove'r with the flanged portion of the button in engagement with the cover when the latch is released and the contact member opens the circuit through the circuit breaker.

10. In an electric circuit breaker, la shell, an elongated member mounted therein for endwise movement, spaced apertured guide means within the shell and slidingly engaging opposite end portions of said elongated member, a pair of spaced contacts within the shell, and a movable contact member cooperating therewith to open and close a circuit therebetween, means operatively connecting said contact member and said elongated member whereby endwise movement of the elongated member is eiective to operate the contact member to circuit closed position, spring means urging the elongated member in a direction in which the contact member is in circuit open position, a latch member mounted on the elongated member and movable therewith, a bimetallic member within the shell and in circuit with said spaced contacts, said bimetallic member including a latch engaging portion normally disposed in the path of movement of said latch member and operable when the latch parts are eng-aged to retain the latch member and said contact member in circuit closing position against movement under the influence of said spring, and eccentric mounting means for one end of said guide means for controllably laterally shifting one end of the elongated member with respect to the other to variably tilt the axis thereof towards and away `from said bimetallic member to thereby vary the degree of overlap between the latch portion oi the bimetallic member and the latch member Iand. thus set the latch for release at different conditions of overload.

EDWARD V, SUNDT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,560,597 Meierjohan Nov. 10, 1925 1,614,169 Aichele Jan. 11, 1927 1,704,379 Aichele Mar. 5, 1929 2,158,387 Taylor May 16, 1939 2,458,807 Tucker Jan. 11, 1949 2,461,338 Miller Feb. 8, 1949 

